What does the Transferrin Saturation (% Saturation) test measure?

Why is Transferrin Saturation (% Saturation) measured?

Transferrin saturation is the primary discriminator in iron panel interpretation. It is particularly critical in distinguishing iron deficiency from anaemia of chronic disease — both produce low serum iron, but transferrin saturation below 16% with high TIBC confirms iron deficiency while transferrin saturation 16–30% with low TIBC in an inflammatory context confirms anaemia of chronic disease. In chronic kidney disease patients on erythropoiesis-stimulating agents (ESA), transferrin saturation below 20% indicates functional iron deficiency requiring iron supplementation regardless of ferritin level. In haemochromatosis screening, transferrin saturation above 45% on fasting specimens warrants HFE gene testing.

Reference ranges

Standard reference

15–50% # REVIEWER FLAG: Confirm Access Medical Laboratories reporting of transferrin saturation — confirm whether it is calculated and reported automatically from serum iron and TIBC, or whether the practitioner calculates it independently. Reference range varies slightly between laboratories.

Functional medicine optimal

20–35% (functional medicine optimal for adequate iron delivery to erythroid marrow without excess). # REVIEWER FLAG: Not standardised as a clinical guideline target — reviewer to confirm framing.

Units

%

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.